1. Field of the Invention
The present invention relates to roller-type reducing apparatus comprising reducing rollers mounted within a housing and adapted to be rotated in opposite directions.
2. Description of the Related Art
Roller-type size reducing apparatus of the inventive kind is used for processing brittle low-abrasion materials, preferably deep-freeze embrittled spent tire fragments, industrial rubber product waste as well as plastics-metal/fiber composites.
Spent motor vehicle tires constitute a rich source of raw materials. In the prior cryogenic process, the rubber of such tires is supposed to be granulated in the embrittled condition for conversion into a reusable secondary raw material which can be returned to production processes.
The rubber granulates and rubber crumbs obtainable in prior cryogenic shredding and reducing plants have turned out to have properties which make them unsuitable for processing and recycling. The granules are too big; they contain excessive amounts of foreign materials that cannot be separated from them any longerxe2x80x94such as steel reinforcements or textile fibersxe2x80x94and are non-uniform in consistency. Scrap rubber of this nature is not suited for large-scale recycling and raises considerable technical problems.
The object of the present invention is to provide for reducing of the type initially described which enables brittle low-abrasion materialsxe2x80x94preferably cryogenically embrittled scrap rubberxe2x80x94to be processed into granulates and powders having a uniform consistency.
This object is attained by using reducing rollers each comprising a plurality of reducing discs placed side by side and having different diameters. In another embodiment, the reducing rollers each comprise a plurality of reducing discs placed side by side and having different diameters and peripheral serrations.
Further, the above object is attained by means of roller-type reducing assembly comprising reducing rollers mounted within a housing for rotation in opposite directions, such rollers comprising differently serrated discs of different diameters and mounted in alternating fashion on associated shafts in such a manner that large-diameter discs of one roller face the small-diameter discs of the other roller.
In addition, the finely serrated reducing discs are provided to have a smaller diameter than the larger-diameter reducing discs.
The aforesaid measures result in roller-type reducing assembly suited for reducing embrittled scrap rubber into rubber granulate and rubber powder. By its design and the materials used for its fabrication, the inventive apparatus will support the special loads and stresses occurring in low-temperature operation at approximately 100xc2x0 C. below freezing.
The rubber component is reduced into a granulate having a relatively uniform granule structure. Most of the fiber and steel component remains in an unreduced condition so that they are easily separated.
The reducing assembly has a closed-loop speed-regulated drive so that the reduction process can be matched closely to the quality of the scrap rubber to be processed. As the reducing gap is variable in width, it is possible to produce a rubber granulate which has a predetermined granule size, granule surface and granule structure. The speeds of the oppositely rotating rollers can be varied independently.
The entire reducing system is arranged for rapid and easy repair and maintenance. To this end, stationary relocating means are provided for relocating the machine components from an operating position to a servicing position using a small number of manual operations. Hoists installed above the servicing position are provided to facilitate necessary repairs.
The reducers are thermally and sound-insulated. In its entirety, the system is encapsulated for operation in a substantially dust-free manner.
Additional advantageous measures are described in the dependent claims. The invention is illustrated in the attached drawings and is described in greater detail below.